Characterization of Al ₂O ₃/InSb/Si MOS diodes having various InSb thicknesses grown on Si(111) substrates

This paper discusses the capacitancevoltage (C-V) characteristics of Al ₂O ₃/InSb/Si (1 1 1) MOS diodes grown using MBE via InSb bi-layer with special care to the surface reconstruction. This growth technique is based on our finding that the InSb layer grown on a Si (1 1 1) substrate is rotated by 30°with respect to the substrate under certain initial conditions. This rotation drastically reduces the lattice mismatch from 19.3% to 3.3%, and improves the crystal quality of an InSb layer. To investigate the possibilities of InSb MOSFETs on Si substrates, we fabricated MOS diodes having an Al ₂O ₃ insulator film deposited by atomic layer deposition. C-V characteristics were measured both at RT and 77 K. It was found that the InSb grown on Si shows a degraded C-V curve compared to the InSb substrate, even though the mobility of the grown layer is quite high. We also investigated the effects of InSb thickness on the C-V characteristics of the MOSFETs. It was found that the quality of MOS diodes first degrades when decreasing the InSb thickness from 1 μm to 50 nm; further reduction of the InSb thickness improves it again. It was demonstrated that the MOS diode having a 10 nm InSb layer shows a good C-V curve, which is comparable to that of the InSb substrate. Finally, we discussed the possibility of the InSb/Si pseudomorphic MOSFETs.